Remote plasma source based cyclic cvd process for nanocrystalline diamond deposition

ABSTRACT

Methods for making a nanocrystalline diamond layer are disclosed herein. A method of forming a layer can include activating a deposition gas comprising an alkane and a hydrogen containing gas at a first pressure, delivering the activated deposition gas to the substrate at a second pressure which is less than the first pressure, forming a nanocrystalline diamond layer, treating the layer with an activated hydrogen containing gas to remove one or more polymers from the surface and repeating the cycle to achieve a desired thickness.

BACKGROUND

1. Field

Embodiments disclosed herein generally relate to methods of forminginert carbon films. More specifically, embodiments generally relate todeposition of nanocrystalline diamond films using a remote plasmasource.

2. Description of the Related Art

As the semiconductor industry introduces new generations of integratedcircuits (IC's) having higher performance and greater functionality, thedensity of the elements that form those IC's is increased, while thedimensions, size and spacing between the individual components orelements are reduced. While in the past such reductions were limitedonly by the ability to define the structures using photolithography,device geometries having dimensions measured in um or nm have creatednew limiting factors, such as the conductivity of the metallic elements,the dielectric constant of the insulating material(s) used between theelements or challenges in 3D NAND or DRAM processes. These limitationsmay be benefitted by more durable and higher hardness hardmasks.

Diamond is known as a high hardness material. Due to high hardness,surface inertness, and low friction coefficient, synthetic diamond hasbeen applied as a protective coating and in microelectromechanicalsystems (MEMS) among other uses. Diamond films, such as nanocrystallinediamond (NCD), have been synthesized by hot filament CVD and microwaveCVD. However, there are a variety of difficulties with hot filament CVDand microwave CVD of nanocrystalline diamond films.

In hot filament CVD, a metal filament is used to activate the precursorgases for deposition. As expected, the metal filament is exposed to theprecursor gases during the film forming process. As a result, precursorgases can react with the metal filament leading to metal contaminationissues in the final product. Compared to hot filament CVD, microwave CVDhas fewer contaminant issues. However microwave CVD requires a highprocess pressure which can affect the film uniformity. Moreover,although microwave plasma from microwave CVD has relatively low energyions, these ions still can attack the NCD grain boundary and inducegrain structure disorder.

Therefore, there is a need for improved methods for diamond filmdeposition.

SUMMARY

Embodiments disclosed herein generally relate to methods of forming adiamond layer. In one embodiment, a method for depositing a layer caninclude performing a deposition process comprising delivering adeposition gas to a remote plasma chamber at a first pressure, thedeposition gas comprising an alkane precursor and a hydrogen containingprecursor; activating the deposition gas to create an activateddeposition gas, the activated deposition gas having a ratio of radicalspecies to ionized species; delivering the activated deposition gasthrough a second volume having a second pressure, the second pressurebeing less than the first pressure, wherein the ratio of radical speciesto ionized species increases in favor of the radical species; deliveringthe activated deposition gas to a substrate in a process volume, theprocess volume having a third pressure, the third pressure being lessthan the second pressure; and depositing a nanocrystalline diamond layeron a surface of the substrate, the nanocrystalline diamond layer havingan upper surface with polymers formed thereon; etching polymers from theupper surface of the nanocrystalline diamond layer; and repeating theperforming of the deposition process and the etching of polymers fromthe surface to deposit a nanocrystalline carbon stack of the desiredthickness.

In another embodiment, a method for depositing a layer can includeperforming a deposition process; performing a hydrogen plasma cleaningprocess; and repeating the performing of the deposition process and thehydrogen plasma cleaning process to deposit a nanocrystalline carbonstack of the desired thickness. The deposition process can includedelivering a deposition gas to a remote plasma chamber at a firstpressure, the deposition gas comprising an alkane precursor and ahydrogen containing precursor; activating the deposition gas to createan activated deposition gas, the activated deposition gas having a ratioof radical species to ionized species; delivering the activateddeposition gas through a second volume having a second pressure, thesecond pressure being less than the first pressure; delivering theactivated deposition gas to a substrate in a process volume, the processvolume having a third pressure, the third pressure being less than thesecond pressure; and depositing a nanocrystalline diamond layer on asurface of the substrate, the nanocrystalline diamond layer. Thehydrogen plasma cleaning process can include delivering a hydrogencontaining gas to a remote plasma chamber; activating the hydrogencontaining gas to create an activated hydrogen containing gas; anddelivering the activated hydrogen containing gas to the substrate in theprocess volume.

In another embodiment, a method for depositing a layer can includepositioning a substrate in the process volume of a processing chamber,the substrate having a preseeded surface; heating the substrate to atemperature of less than 500 degrees Celsius; performing a depositionprocess; and repeating the performing of the deposition process todeposit a nanocrystalline carbon stack of the desired thickness. Thedeposition process can include delivering a deposition gas to a remoteplasma chamber at a first pressure between 10 Torr and 100 Torr, thedeposition gas comprising methane and hydrogen gas; delivering RF powerto activate the deposition gas, creating an activated deposition gas,the RF power being between 1000 W and 3000 W, the activated depositiongas having a ratio of radical species to ionized species; delivering theactivated deposition gas through a second volume having a secondpressure between 1 Torr and 5 Torr; delivering the activated depositiongas to a substrate in a process volume, the process volume having athird pressure between 500 mTorr and 1 Torr; and depositing ananocrystalline diamond layer on a surface of the substrate, thenanocrystalline diamond layer having sp2 bonds and sp3 bonds; deliveringthe hydrogen gas in the absence of the methane to a remote plasmachamber; activating the hydrogen gas to create an activated hydrogengas; and delivering the activated hydrogen gas to a substrate in aprocess volume.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic cross-sectional view of a CVD process chamberconfigured according to one or more embodiments; and

FIGS. 2A and 2B are flow diagrams of a method for forming ananocrystalline diamond layer, according to one or more embodiments.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Embodiments disclosed herein generally relate to forming acarbon-containing layer, such as a nanocrystalline diamond layer, on asubstrate. By forming the reactive species remotely and under highpressure the ratio of radicals versus ionized species can be skewedpreferentially towards the radical species. The radical species can thenbe delivered to the substrate to deposit a nanocrystalline diamond layerwith preferentially sp3 bonding. Embodiments are more clearly describedwith reference to the figures below.

FIG. 1 is a schematic cross-sectional view of a CVD process chamber 100that may be used for depositing a carbon based layer according to theembodiments described herein. A process chamber 100 is available fromApplied Materials, Inc. located in Santa Clara, Calif., and a briefdescription thereof follows. Processing chambers that may be adapted toperform the carbon layer deposition methods described herein is thePRODUCER® chemical vapor deposition chamber, both available from AppliedMaterials, Inc. located in Santa Clara, Calif. It is to be understoodthat the chamber described below is an exemplary embodiment and otherchambers, including chambers from other manufacturers, may be used withor modified to match embodiments of this invention without divergingfrom the inventive characteristics described herein.

The process chamber 100 may be part of a processing system (not shown)that includes multiple processing chambers connected to a centraltransfer chamber (not shown) and serviced by a robot (not shown). Theprocess chamber 100 includes walls 106, a bottom 108, and a lid 110 thatdefine a process volume 112. The walls 106 and bottom 108 can befabricated from a unitary block of aluminum. The process chamber 100 mayalso include a pumping ring 114 that fluidly couples the process volume112 to an exhaust port 116 as well as other pumping components (notshown).

A substrate support assembly 138, which may be heated, may be centrallydisposed within the process chamber 100. The substrate support assembly138 supports a substrate 103 during a deposition process. The substratesupport assembly 138 generally is fabricated from aluminum, ceramic or acombination of aluminum and ceramic, and includes at least one biaselectrode 132.

A vacuum port may be used to apply a vacuum between the substrate 103and the substrate support assembly 138 to secure the substrate 103 tothe substrate support assembly 138 during the deposition process. Thebias electrode 132, may be, for example, the electrode 132 disposed inthe substrate support assembly 138, and coupled to a bias power source130A and 130B, to bias the substrate support assembly 138 and substrate103 positioned thereon to a predetermined bias power level whileprocessing.

The bias power source 130A and 130B can be independently configured todeliver power to the substrate 103 and the substrate support assembly138 at a variety of frequencies, such as a frequency between about 1 andabout 60 MHz. In one embodiment, the bias power source 130A may beconfigured to deliver power to the substrate 103 at a frequency of about2 MHz and the bias power source 130B may be configured to deliver powerto the substrate 103 at a frequency of about 13.56 MHz. In anotherembodiment, the bias power source 130A may be configured to deliverpower to the substrate 103 at a frequency of 2 MHz, the bias powersource 130B may be configured to deliver power to the substrate 103 at afrequency of 13.56 MHz and a third power source (not shown) isconfigured to deliver power to the substrate 103 at a frequency of about60 MHz. Various permutations of the frequencies described here can beemployed without diverging from the invention described herein.

Generally, the substrate support assembly 138 is coupled to a stem 142.The stem 142 provides a conduit for electrical leads, vacuum and gassupply lines between the substrate support assembly 138 and othercomponents of the process chamber 100. Additionally, the stem 142couples the substrate support assembly 138 to a lift system 144 thatmoves the substrate support assembly 138 between an elevated position(as shown in FIG. 1) and a lowered position (not shown) to facilitaterobotic transfer. Bellows 146 provide a vacuum seal between the processvolume 112 and the atmosphere outside the chamber 100 while facilitatingthe movement of the substrate support assembly 138.

The showerhead 118 may generally be coupled to an interior side 120 ofthe lid 110. Gases (i.e., process and other gases) that enter theprocess chamber 100 pass through the showerhead 118 and into the processchamber 100. The showerhead 118 may be configured to provide a uniformflow of gases to the process chamber 100. Uniform gas flow is desirableto promote uniform layer formation on the substrate 103. A remote plasmasource 105 can be coupled with the process volume 112. Shown here, aremote activation source, such as a remote plasma generator, is used togenerate a plasma of reactive species which are then delivered into theprocess volume 112. Exemplary remote plasma generators are availablefrom vendors such as MKS Instruments, Inc. and Advanced EnergyIndustries, Inc.

Additionally, a plasma power source 160 may be coupled to the showerhead118 to energize the gases through the showerhead 118 towards substrate103 disposed on the substrate support assembly 138. The plasma powersource 160 may provide RF power.

The function of the process chamber 100 can be controlled by a computingdevice 154. The computing device 154 may be one of any form of generalpurpose computer that can be used in an industrial setting forcontrolling various chambers and sub-processors. The computing device154 includes a computer processor 156. The computing device 154 includesmemory 158. The memory 158 may include any suitable memory, such asrandom access memory, read only memory, flash memory, hard disk, or anyother form of digital storage, local or remote. The computing device 154may include various support circuits 160, which may be coupled to thecomputer processor 156 for supporting the computer processor 156 in aconventional manner. Software routines, as required, may be stored inthe memory 156 or executed by a second computing device (not shown) thatis remotely located.

The computing device 154 may further include one or more computerreadable media (not shown). Computer readable media generally includesany device, located either locally or remotely, which is capable ofstoring information that is retrievable by a computing device. Examplesof computer readable media 154 useable with embodiments of the presentinvention include solid state memory, floppy disks, internal or externalhard drives, and optical memory (CDs, DVDs, BR-D, etc). In oneembodiment, the memory 158 may be the computer readable media. Softwareroutines may be stored on the computer readable media to be executed bythe computing device.

The software routines, when executed, transform the general purposecomputer into a specific process computer that controls the chamberoperation so that a chamber process is performed. Alternatively, thesoftware routines may be performed in hardware as an applicationspecific integrated circuit or other type of hardware implementation, ora combination of software and hardware.

FIGS. 2A and 2B are a flow diagram of a method 200 for forming ananocrystalline diamond layer, according to one or more embodiments. Byactivating the deposition gas at a high pressure, the quantity ofionized species in the activated deposition gas is reduced as comparedto low pressure. The pressure in the activated deposition gas can thenbe lowered such that better deposition uniformity is achieved. Polymers,which are formed during the deposition process, can then be removed fromthe layer surface before repeating the deposition process.

The method 200 begins at 202 by delivering a deposition gas to a remoteplasma chamber at a first pressure, at 202. The deposition gas includesa carbon-containing precursor and a hydrogen containing gas. In thisembodiment, the carbon-containing precursor is an alkane precursor. Thealkane precursor can be a saturated unbranched hydrocarbon, such asMethane, Ethane, Propane, and combinations thereof. Other alkaneprecursors include n-Butane, n-Pentane, n-Hexane, n-Heptane, n-Octane,and combinations thereof. The hydrogen containing gas can include H₂,H₂O, NH₃ or other hydrogen containing molecules. The deposition gas canfurther include an inert gas. The inert gas can be a noble gas, such asargon.

The deposition gas is then delivered to the remote plasma chamber. Thedeposition gas can either mix within the chamber or be mixed prior toentering the chamber. The deposition gas is delivered at a relativelyhigh pressure, such as greater than 5 Torr. In one embodiment, thedeposition gas is delivered at between about 10 Torr and 100 Torr, suchas about 50 Torr.

The deposition gas can then be activated to create an activateddeposition gas, at 204. The deposition gas can be activated by forming aplasma using a power source. Any power source capable of activating thegases into reactive species and maintaining the plasma of reactivespecies may be used. For example, radio frequency (RF), direct current(DC), or microwave (MW) based power discharge techniques may be used.The power source produces a source plasma power which is applied to theremote plasma chamber to generate and maintain a plasma of thedeposition gas. In embodiments which use an RF power for the sourceplasma power, the source plasma power can be delivered at a frequency offrom about 2 MHz to about 170 MHz and at a power level of between 500 Wand 5000 W, for a 300 mm substrate (between 0.56 W/cm² of the topsurface of the substrate and 5.56 W/cm² of the top surface of thesubstrate). Other embodiments include delivering the source plasma powerat from about 1000 W to about 3000 W, for a 300 mm substrate (from 1.11W/cm² of the top surface of the substrate to 3.33 W/cm² of the topsurface of the substrate). The power applied can be adjusted accordingto size of the substrate being processed.

Based on the high pressure in the remote plasma chamber as well as otherfactors, ionized species formation will be minimized while radicalformation is maximized. Without intending to be bound by theory, it isbelieved that the nanocrystalline diamond layer should be primarily sp3bonds rather than sp2 bonds. Further, it is believed that more sp3bonding can be achieved by increasing the number of radical species overionized species during the deposition of the layer. Ionized species arehighly energetic can need more room for movement than radicals. Byincreasing the pressure, electron energy is reduced while the likelihoodof collision with other molecules increases. The decrease in electronenergy and increase in number of collisions favors radical formationover ion formation.

Once activated, the activated deposition gas is then delivered through asecond volume having a second pressure, at 206. The second volume can bea second chamber or another confined area between the process volume andthe remote plasma chamber. In one example, the second volume is theconnection between the remote plasma chamber and the process volume.

The second pressure is less than the first pressure. The movement fromthe remote plasma chamber to the second volume either based on flowrate, change in overall volume or combinations thereof results in areduced pressure of the activated deposition gas in the second volume.The pressure is reduced to allow for better deposition from the radicalspecies while reducing ionized species collision with the depositedlayer. In one embodiment, the second pressure is between about 1 Torrand about 5 Torr.

The activated deposition gas is then delivered to a substrate in aprocess volume of a processing chamber, at 208. The substrate can be ofany composition, such as a crystalline silicon substrate. The substratecan also include one or more features, such as a via or an interconnect.The substrate can be supported on a substrate support. The substratesupport can be maintained in a specific temperature range. In oneembodiment, the substrate support is maintained in a temperature rangeof between about 500 degrees Celsius and about 650 degrees Celsius.

The substrate can be preseeded for deposition of the nanocrystallinelayer. In one embodiment, the substrate is immersed or otherwise coatedin a seeding solution. The seeding solution is an ethanol basednanodiamond suspension. The substrate is immersed in the suspensionduring an ultrasonic treatment, which adheres some of the suspendednanodiamonds to the surface of the substrate. Other preseedingtechniques can be employed without diverging from the embodimentsdescribed herein.

The processing chamber used with one or more embodiments can be any CVDprocessing chamber with a remote plasma source, such as the processingchamber 100 described above or chambers from other manufacturers. Flowrates and other processing parameters described below are for a 300 mmsubstrate. It should be understood these parameters can be adjustedbased on the size of the substrate processed and the type of chamberused without diverging from the invention disclosed herein.

A “substrate surface”, as used herein, refers to any substrate ormaterial surface formed on a substrate upon which film processing isperformed. For example, a substrate surface on which processing can beperformed includes materials such as silicon, silicon oxide, siliconnitride, doped silicon, germanium, gallium arsenide, glass, sapphire,and any other materials such as metals, metal nitrides, metal alloys,and other conductive materials, depending on the application. Asubstrate surface may also include dielectric materials such as silicondioxide and carbon doped silicon oxides. Substrates may have variousdimensions, such as 200 mm, 300 mm or other diameter wafers, as well asrectangular or square panes.

The process volume receives the activated deposition gas at a thirdpressure, which is less than the second pressure. The third pressure canbe a pressure less than 2 Torr, such as a pressure of between about 500mTorr and 1 Torr.

A nanocrystalline diamond layer is then deposited on a surface of thesubstrate, at 210. The radicals from the previously formed activateddeposition gas impinge on the substrate surface to form thenanocrystalline diamond layer. Low pressure is believed to be beneficialto the formation of sp3 bonding in the nanocrystalline diamond layerfrom the remotely formed radicals. The higher pressure in the remoteplasma source allows for preferential radical formation while the lowerpressure in the process volume allows for more uniform deposition fromthe previously formed radicals.

Once the nanocrystalline diamond layer is deposited, a hydrogencontaining gas is delivered to the remote plasma chamber, at 212. Thehydrogen containing gas can be delivered at a separate time or the gasflow from the previous step can be maintained. No alkane precursor ispresent for this portion. The hydrogen containing gas can be deliveredwith an inert gas or as part of a combination of multiple hydrogencontaining gases.

The hydrogen containing gas is then activated to create an activatedhydrogen containing gas, at 214. The hydrogen containing gas can beconverted to a plasma using the same pressure, temperature, power type,power ranges and other parameters for formation of the plasma discussedwith reference to forming the activated deposition gas.

Once the activated hydrogen containing gas is formed, it can bedelivered to the substrate in the process volume, at 216. The processvolume and the substrate may be maintained at the same pressure,temperature and other parameters as described above. During thedeposition process, it is believed that polymers can form on the surfaceof the deposited nanocrystalline diamond layer. The polymers can affectfurther deposition and otherwise degrade performance of the depositedlayer. By delivering the activated hydrogen containing gas to thedeposited layer, the polymers are made volatile and can then be removedfrom the chamber, such that they do not affect subsequent depositionprocesses.

The above elements can then be repeated to deposit a nanocrystallinediamond stack of a desired thickness, at 218. Each deposition cycleproduces a thickness of between about 20 Å and about 200 Å, such asabout 100 Å. By repeating the above steps, the previous layer acts as aseed layer for the next deposition, allowing for an overall desiredthickness to be deposited. In one embodiment, the nanocrystallinediamond stack is deposited to 1 μm thick.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for depositing a layer, comprising: performing a depositionprocess comprising: delivering a deposition gas to a remote plasmachamber at a first pressure, the deposition gas comprising: an alkaneprecursor; and a hydrogen containing precursor; activating thedeposition gas to create an activated deposition gas, the activateddeposition gas having a ratio of radical species to ionized species;delivering the activated deposition gas through a second volume having asecond pressure, the second pressure being less than the first pressure,wherein the ratio of radical species to ionized species increases infavor of the radical species, delivering the activated deposition gas toa substrate in a process volume, the process volume having a thirdpressure, the third pressure being less than the second pressure; anddepositing a nanocrystalline diamond layer on a surface of thesubstrate, the nanocrystalline diamond layer having an upper surfacewith polymers formed thereon; etching polymers from the upper surface ofthe nanocrystalline diamond layer; and repeating the performing adeposition process and the etching polymers from the upper surface todeposit a nanocrystalline carbon stack of a desired thickness.
 2. Themethod of claim 1, wherein the first pressure is between about 10 Torrand about 100 Torr.
 3. The method of claim 1, wherein the substrate ismaintained at a temperature range of between about 500 degrees Celsiusand about 650 degrees Celsius.
 4. The method of claim 1, wherein thesecond pressure is between about 1 Torr and about 5 Torr.
 5. The methodof claim 1, wherein the third pressure is between about 500 mTorr andabout 1 Torr.
 6. The method of claim 1, wherein the deposition gas isactivated using an RF source.
 7. The method of claim 6, wherein the RFsource provides power between about 1000 W and 3000 W.
 8. The method ofclaim 1, wherein the polymers are etched from the upper surface using ahydrogen plasma.
 9. The method of claim 1, wherein the surface of thesubstrate is preseeded.
 10. The method of claim 1, wherein the alkane ismethane.
 11. A method for depositing a layer, comprising: performing adeposition process comprising: delivering a deposition gas to a remoteplasma chamber at a first pressure, the deposition gas comprising: analkane precursor; and a hydrogen containing precursor; activating thedeposition gas to create an activated deposition gas, the activateddeposition gas having a ratio of radical species to ionized species;delivering the activated deposition gas through a second volume having asecond pressure, the second pressure being less than the first pressure;delivering the activated deposition gas to a substrate in a processvolume, the process volume having a third pressure, the third pressurebeing less than the second pressure; and depositing a nanocrystallinediamond layer on a surface of the substrate, the nanocrystalline diamondlayer; performing a hydrogen plasma cleaning process, comprising:delivering a hydrogen containing gas to a remote plasma chamber;activating the hydrogen containing gas to create an activated hydrogencontaining gas; and delivering the activated hydrogen containing gas tothe substrate in the process volume; and repeating the performing of thedeposition process and the hydrogen plasma cleaning process to deposit ananocrystalline carbon stack of the desired thickness.
 12. The method ofclaim 11, wherein the first pressure is between about 10 Torr and about100 Torr.
 13. The method of claim 11, wherein the substrate ismaintained at a temperature range of between about 500 degrees Celsiusand about 650 degrees Celsius.
 14. The method of claim 12, wherein thesecond pressure is between about 1 Torr and about 5 Torr.
 15. The methodof claim 14, wherein the third pressure is between about 500 mTorr andabout 1 Torr.
 16. The method of claim 11, wherein the deposition gas isactivated using an RF source, and wherein the RF source provides powerbetween about 1000 W and 3000 W.
 17. The method of claim 11, wherein thedelivery of the activated deposition gas transitions to the delivery ofthe activated hydrogen containing gas without interruption in gas flow.18. The method of claim 11, wherein the surface of the substrate ispreseeded.
 19. The method of claim 11, wherein the alkane is methane.20. A method for depositing a layer, comprising: positioning a substratein the process volume of a processing chamber, the substrate having apreseeded surface; heating the substrate to a temperature of less than500 degrees Celsius; performing a deposition process comprising:delivering a deposition gas to a remote plasma chamber at a firstpressure between 10 Torr and 100 Torr, the deposition gas comprisingmethane and hydrogen gas; delivering RF power to activate the depositiongas, creating an activated deposition gas, the RF power being between1000 W and 3000 W, the activated deposition gas having a ratio ofradical species to ionized species; delivering the activated depositiongas through a second volume having a second pressure between 1 Torr and5 Torr; delivering the activated deposition gas to a substrate in aprocess volume, the process volume having a third pressure between 500mTorr and 1 Torr; and depositing a nanocrystalline diamond layer on asurface of the substrate, the nanocrystalline diamond layer having sp2bonds and sp3 bonds; delivering the hydrogen gas in the absence of themethane to a remote plasma chamber; activating the hydrogen gas tocreate an activated hydrogen gas; delivering the activated hydrogen gasto a substrate in a process volume; and repeating the performing of thedeposition process to deposit a nanocrystalline carbon stack of thedesired thickness.